A conventional wooden pallet is made up of a plurality of stringer members which are sandwiched between a plurality of slats. The slat members are traversely arranged with respect to the stringers, and attached to the tops and bottoms of the stringers by automatic nailing machines. The stringers all have a pair of notches cut along their bottom edge for receipt of the forks of a lift truck so that the pallet can be picked up from any side.
While pallet stringer notches were originally hand-cut, there have been numerous machines in recent years which automatically cut the notches as the stringers are forced through a machine in adjacent side-by-side relation. Examples of these machines are illustrated in U.S. Pat. Nos. 3,470,924 and 3,664,394. The first mentioned patent drives a row of pre-aligned stringers past a rotating horizontally positioned cutting head which grinds away the entire area of the notch in an action similar to a routing tool. The second patent mentioned incorporates a gang of vertically positioned dado blades which also grind away the entire area of the notch. One of the above-mentioned methods require that the stringers be stacked one behind the other and firmly held during the cutting operation to keep from tearing and splitting. Both of these patents require a substantial amount of power and holding force on the stringers since they grind away the entire notch area.
An advancement in the state of the art over the two above-mentioned patents is applicant's own U.S. Pat. No. 4,132,253. The basic advantage of this patent is the utilization of substantially less power by making a series of saw cuts in place of the grinding method of the two prior art systems mentioned. Still, in this patent, as in the other two patents, it was felt that the notches had to be cut in the stringer members prior to assembly of the pallet.
Most pallet assembly lines today include a nailing machine; a turning machine; sometimes a second nailing machine, and a stacking machine for the completed pallet at the end of the assembly process. At the first nailing machine, the operators are provided with stacks of pre-cut slats and pre-notched stringers which are laid out for the nailing machine to fasten one side at a time. If only one nailing machine is used in the line, the pallet must be run through the nailing machine a second time after it is turned so that the slats on the opposite side may be attached. The stack of pre-cut and notched stringers requires a notching machine similar to one of those mentioned above along with at least two operators.
The method of the present invention notches the pallet stringers after the pallet is constructed in the assembly line process, thereby eliminating two operators which previously manned the notching machine when the stringers were notched before assembly of the pallet. Due to the relatively light forces involved and energy utilized with saw cuts in place of grinding, it has become possible to cut stringer notches in an already made-up pallet. Prior to the present invention it was felt that this was not possible in light of the forces involved and amount of splitting and tearing of the stringer during formation of the notch.
A principal object of the present invention is to provide a new and improved method for notching pallets which minimizes the operators necessary for operation of the machine.
Another object of the present invention is to provide an automated notching machine which cuts a pair of notches in the stringers of a pre-assembled pallet on a single pass through the machine.